1. Proof of Concept Collaboration #1
Using Cross-jurisdictional Data Linkage to Investigate Cross-Border Hospital Use
Presented by Katrina Spilsbury
Centre for Population Health Research, Curtin University

2. Why Cross-jurisdictional Linkage of Health Data?
Accurate data for longitudinal studies
People who move frequently or die interstate
Seasonal or out of state workers
Increase statistical power to research rare diseases or health outcomes
Evaluate state-based variations in hospital care

3. Is cross-border hospital use really an issue?
Darwin NT
QLD
NSW
QLD
Brisbane WA
Brisbane SA
NSW
& ACT
Perth
Sydney
Adelaide
VIC
Melbourne
Hobart
= Hospital
TAS
Source: Australian Bureau of Statistics

4. PoC #1 – Aims Epidemiological Technical / Logistical
Cross-border hospital use – size of the issue?
Can cross-jurisdictional linkage refine estimates of hospital-related mortality?
Technical / Logistical
Data handling and cleaning issues
Standardisation of data
What can be improved or streamlined?

5. PoC #1 – Data WA, NSW, QLD & SA participating jurisdictions
Five years of data – July 2004 to June 2009
Hospital records
Public and private hospital in-patient (WA, NSW and QLD)
Public hospital in-patient (SA)
Death records – WA, NSW, QLD & SA

6. Data Separation Principle
State Data Linkage Units
& Data Custodians
Centre for Data Linkage
Researcher
Keys
Key Name Dob
AAA Joe Blow 1930
BBB May Wind 1980
Year Clinical info
2003 Poorly
2005 Very poorly
2006 Died
2002 1st child
2004 Twins
Keys Names DOB
Keys
XXX
AAA
BBB
YYY
Name Dob Key
Joe Blow
May Wind
NSW
Key Year Clinical info
Broken arm
Poorly
Very poorly
Died
st child
Twins
Triplets
Exhaustion
Keys
Clinical Info
Keys
Clinical Info
Keys Names DOB SA
Key Name Dob
XXX Joe Blow 1930
YYY May Wind 1980
Year Clinical info
2000 Broken arm
2007 Triplets
2008 Exhaustion
Keys

7. Data cleaning Reformatting file types Renaming and recoding variables
Applying exclusion criteria
Funding duplicates, cancelled procedures, boarders, organ procurements, healthy newborns
Records missing age, sex, principal diagnosis or separation mode
Non-Australian postcodes of residence.
1.4 million out of 38 million hospital records
excluded

8. Excluded episodes of care (hospital records)
Data cleaning by state
Excluded episodes of care (hospital records)
NSW WA
QLD SA
Total excluded
Potential funding duplicate records – one kept
31,345
9,358
964
20,903
Missing age at admission
842
Missing sex or intersex
199 3 6
211
Missing principal diagnosis
28,738
Newborn3, boarder, organ procurement care types
604,128
36,473
427,795
22,042
1,090,438
Non-hospital facility (rehab, nursing, hospices)
149,416
13,447
1,879
164,742
Non-medical hospital encounter (Z76)
1,899
4,137
1,496
760
8,292
Cancelled procedures (Z53)
1,609 35
1,644
Missing, unknown or overseas postcodes
84,888
8,412
30,788
3,267
127,355
Separation date < admission date or missing
125
Total excluded
903,189
49,025
482,925
28,915
1,443,290

9. Coding variation between states
NSW WA
QLD SA N %
Day case chemotherapy (Z51.1)
Public hospital
26,784
11.5
150,826
53.5
180,891
36.0
63,606
100
Private hospital
206,693
88.5
131,011
46.5
321,812
64.0 -
Day case renal dialysis (Z49.1)
Elective
1,606,258
91.5
57,316
4.7
Emergency
12,581
0.7
290
0.02
Not assigned
136,494
7.8
729,104
1,159,719
95.3
313,774
100.0
Single delivery (O80)
25,798
30.4
0.0
1,866
2.7
2,155
2.5
6,472
9.5
57,029
67.1
23,983
59,521
87.7
11,205
ED deaths recorded as in-patient
Yes No

10. PoC #1 – Findings Acute care hospital stays
Multi-episodes of care (records) bought together
SA – Public Hospitals only
NSW WA
QLD SA
Total N %
All Hospital stays
8,723,879
46.2
2,799,646
14.8
5,919,025
31.4
1,427,780
7.6
18,870,330
All Individuals
3,660,991
47.9
1,094,303
14.3
2,286,449
30.0
608,921
8.0
7,650,664
Public Hospital Stays 
In-hospital deaths
95,735
1.8
19,177
1.2
40,929
1.4
20,073
175,913
30 day deaths
30,733
6,409
1.1
12,047
7,922
1.3
66,324

11. Hospital Stays by Travellers Jurisdiction of hospital stay
223,262 (3.0%) individuals who had 352,969 (1.9%) hospital stays as traveller
Residence
Jurisdiction of hospital stay
NSW WA
QLD SA
Total -
3,111
131,149
5,986
140,246
3,550
2,536
1,260
7,346
65,506
2,612
1,606
69,724
3,798
1,195
2,964
7,957
VIC
59,967
2,716
12,131
9,594
84,408
TAS
2,269
418
1,850
369
4,906 NT
1,890
1,593
3,862
8,627
15,972
ACT
20,871
189
1,128
222
22,410
157,851 (1.81%)
11,834 (0.42%)
155,620 (2.63%)
27,664 (1.94%)
352,969 (1.87%)

12. Residence of Travellers
Jurisdiction of residence

13. Hospital Stays by Movers Jurisdiction of post-move residence
There were 48,575 (0.6%) individuals with 59,387 hospital stays recorded as movers
Pre-move
residence
Jurisdiction of post-move residence
NSW WA
QLD SA
Total -
3,719
19,549
1,832
25,100
2,854
3,988
1,168
8,010
12,835
3,143
1,520
17,498
1,568
1,173
1,917
4,658
VIC
970
216
591
286
2,063
TAS
105 35 94 15
249 NT
154
220
299
257
930
ACT
700 34
125 20
879
19,186 (0.22%)
8,540 (0.31%)
26,563 (0.45%)
5,098 (0.36%)
59,387 (0.31%)

14. Residence of Movers Jurisdiction pre-move
Note: By definition a mover had at least 2 hospital stays over a 5 year period

15. Cross-border hospital transfers Jurisdiction of receiving hospital
Over 11,000 acute care hospital transfers across state borders of the four jurisdictions were identified
Jurisdiction
of sending hospital
Jurisdiction of receiving hospital
NSW WA
QLD SA
Total  - 12
8,114
1,316
9,442 27 -  26 65
1258 8
1,278
299 24
331
1,584 28
8,164
1,340
11,116

16. Cross-border hospital transfers
Jurisdiction of sending hospital

17. Conclusion Cross-border hospital use
SA & QLD receive highest proportions of patients from elsewhere
Mining / tourism regions in QLD & WA have high numbers of movers
Cross-jurisdictionally linked data is complex!
Very large files
Takes time to understand
Local knowledge and input essential
Centralised approach to data and metadata?

18. PoC #1 - Contributors
Centre for Data Linkage (WA)
Anna Ferrante, James Boyd, Sean Randall & Jacqui Bauer
Queensland
Ben Wilkinson, Trisha Johnston & Ann Harrington– QLD Health
Julie Hall and Erica Findlay – QLD Births Deaths Marriages,
PHRN Program Office
Merran Smith, Felicity Flack, Angela Young, Nathalie Wray,
Emma Fuller & Tony Woollacott
Others
Vicky Stagg - University of Calgary, Canada
James Harrison – Flinders University
Bruce Armstrong – University of Sydney
Neville Board – ACSQHC
Robyn Munro & Alan Finlayson – NS, Scotland
Sanja Lujic – University of Western Sydney
Research team (WA)
Katrina Spilsbury & Janine Alan – Centre for Population Health Research, Curtin University
Di Rosman – WA Health
New South Wales
Lee Taylor, Kim Lim, Baohui Yang and Zoran Bolevich– NSW Ministry of Health
South Australia
Almond Sparrow and Stacy Vasquez – SA NT Data Link
Paul Basso, Tina Hardin & Tomi Adejoro – SA Health
Helen Paues – SA Births Deaths and Marriages
Darren Shaw – Promadis
Western Australia
Jessica Lee, Alex Godfrey, Paul Stevens & Carol Garfield - WA Health
Brett Burns – WA Births, Deaths & Marriages,
This project was jointly supported by the Australian Government’s National Collaborative Research Infrastructure Strategy and the Western Australian Department of Commerce